CN109905033B - Transformer unit and method for operating a transformer unit - Google Patents
Transformer unit and method for operating a transformer unit Download PDFInfo
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- CN109905033B CN109905033B CN201811407351.9A CN201811407351A CN109905033B CN 109905033 B CN109905033 B CN 109905033B CN 201811407351 A CN201811407351 A CN 201811407351A CN 109905033 B CN109905033 B CN 109905033B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05G—X-RAY TECHNIQUE
- H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
- H05G1/08—Electrical details
- H05G1/26—Measuring, controlling or protecting
- H05G1/30—Controlling
- H05G1/32—Supply voltage of the X-ray apparatus or tube
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05G—X-RAY TECHNIQUE
- H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
- H05G1/08—Electrical details
- H05G1/10—Power supply arrangements for feeding the X-ray tube
- H05G1/14—Power supply arrangements for feeding the X-ray tube with single-phase low-frequency ac also when a rectifer element is in series with the X-ray tube
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05G—X-RAY TECHNIQUE
- H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
- H05G1/08—Electrical details
- H05G1/26—Measuring, controlling or protecting
- H05G1/265—Measurements of current, voltage or power
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05G—X-RAY TECHNIQUE
- H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
- H05G1/08—Electrical details
- H05G1/26—Measuring, controlling or protecting
- H05G1/30—Controlling
- H05G1/48—Compensating the voltage drop occurring at the instant of switching-on of the apparatus
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05G—X-RAY TECHNIQUE
- H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
- H05G1/08—Electrical details
- H05G1/26—Measuring, controlling or protecting
- H05G1/54—Protecting or lifetime prediction
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Abstract
A transformer unit and a method for operating a transformer unit are proposed. The transformer unit has a primary side with a primary winding and a secondary side with a secondary winding, wherein during operation when the primary winding is loaded with a primary voltage, an actual voltage on the secondary side occurs, which is influenced by an additional voltage drop on the secondary side, which is dependent on parasitic effects on the secondary side. The transformer unit also has a first measuring coil wound around the transformer core for determining a first measuring voltage, and a measuring element which is arranged and designed on the primary side in such a way that a second measuring voltage associated with a voltage drop on the secondary side is determined via the measuring element. The transformer unit also has a control unit, wherein the control unit is designed to regulate the primary voltage in order to induce a predetermined secondary desired voltage in the secondary winding and to regulate the primary voltage as a function of the first and second measured voltages.
Description
Technical Field
The present invention relates to a transformer unit, in particular for providing a voltage for an X-ray tube arrangement, and to a method for operating a transformer unit.
Background
Imaging devices, for example in medical diagnostics, usually have an X-ray tube arrangement for generating X-ray radiation. In order to generate radiation, a voltage is applied between a cathode and an anode of the X-ray tube device, whereby electrons are accelerated from the cathode towards the anode and the desired X-ray radiation is released when impinging on the anode.
The voltage usually has a value in the range of several kilovolts and is typically generated by means of a transformer unit.
A transformer typically has a primary side with a primary coil and a secondary side with a secondary coil. The two coils (primary and secondary) are wound around a common transformer core. The transformer core usually has a ferromagnetic material with a high magnetic permeability. The two coils are magnetically coupled to each other by the transformer core. With the application of a primary or excitation voltage, a secondary voltage is induced in the secondary coil. When an electrical load, for example an X-ray tube arrangement, is applied to the secondary coil, a secondary current also flows therein.
The value of the induced secondary voltage is determined by the so-called winding ratio of the two coils.
In operation, the secondary voltage is regulated to a desired voltage on the secondary side by adjusting the value of the primary voltage.
Due to losses within the transformer unit, it is costly to adjust the desired voltage on the desired secondary side with high accuracy. The loss is usually a so-called leakage flux loss. Currently, leakage losses are generally understood to be the part of the magnetic flux that does not penetrate the secondary coil and thus does not contribute to the induction of the secondary coil. Further types of losses within the transformer unit are, for example, copper losses, which are caused by the material resistance of the coil, which is preferably made of copper, or capacitive losses, which occur between adjacent windings, which act as capacitors with respect to one another. Leakage losses and capacitive losses are also commonly referred to as parasitic losses.
The losses, in particular the leakage losses, cause an undesirable voltage drop during operation of the transformer unit. Thus, for example, the actual secondary voltage (actual voltage on the secondary side) has a smaller value than the ideal secondary voltage which can be expected by the primary voltage and the winding ratio in an ideal, loss-free transformer unit. The value of the actual secondary-side actual voltage (ideal secondary voltage minus an additional voltage drop due to leakage losses) can deviate from the ideal secondary voltage by several hundred volts in relation to the preset secondary voltage.
Said high deviations are undesirable in particular in X-ray systems. The regulation is carried out, for example, as a function of the actual voltage on the secondary side, so that the actual voltage is detected on the secondary side and is transmitted to the primary side, and the primary voltage is then (post-) regulated as a function of the actual voltage. However, this design is costly and cost-intensive. Alternatively, a predetermined secondary voltage is detected on the primary side, wherein, however, an additional voltage drop on the secondary side caused by parasitic effects cannot be detected. Therefore, the actual voltage of the secondary side cannot be accurately determined.
Disclosure of Invention
Starting from this, the invention is based on the object of specifying a transformer unit and a method by means of which the actual voltage on the secondary side can be provided in a simple manner with sufficient accuracy.
The object is achieved according to the invention by a transformer unit having the features of the invention. Advantageous embodiments, improvements and variants are the subject matter of the following description.
The transformer unit has a primary side with a primary coil wound around a transformer core and a secondary side with a secondary coil also wound around the transformer core.
According to the general functional principle of the transformer unit, the primary side and the secondary side are electrically separated from each other and magnetically coupled to each other. Electrical separation is currently understood generally as: the primary side and the secondary side are in particular not connected by wires, for example electrically connected to each other by means of wires. Thus, the primary side and the secondary side are galvanically separated from each other.
In operation of the transformer unit, when the primary winding is charged with the primary voltage, the actual voltage on the secondary side occurs. The primary voltage is currently understood to be an alternating voltage. The actual voltage on the secondary side is influenced in particular by an additional voltage drop on the secondary side, which depends on parasitic effects on the secondary side. In other words, the actual voltage on the secondary side can be changed, in particular reduced, by the additional voltage drop on the secondary side with respect to the predetermined desired voltage on the secondary side.
The transformer unit also has a first measuring coil wound around the transformer core, which is used to determine a first measuring voltage. The first measured voltage is currently understood to be, in particular, the desired voltage of the secondary. Preferably, the first measuring coil is arranged in a subregion of the primary side of the transformer unit. I.e. the first measuring coil is located closer in location to the primary coil than to the secondary coil. This arrangement of the first measuring coil has proven to be suitable for detecting the desired voltage of the secondary at the primary side.
The transformer unit also has a measuring element. The measuring element is arranged and designed on the primary side in such a way that a second measuring voltage is determined via the measuring element, said second measuring voltage being associated with an additional voltage drop, in particular a leakage inductance, on the secondary side. The arrangement of the measuring element on the primary side is based on the following considerations: due to the magnetic coupling of the primary side and the secondary side, parasitic effects on the secondary side also act on the primary side. The parasitic effects, in particular leakage magnetic effects on the secondary side (caused, for example, by leakage inductances), can thus be detected by means of the second measurement voltage on the primary side. I.e. the second measurement voltage, can be said to be the already mentioned additional voltage drop on the secondary side, in particular the electron microscope image of the leakage inductance on the primary side.
In order to control the operation of the transformer unit, in particular to supply the X-ray tube device voltage, the transformer unit has a control unit. The X-ray tube device voltage is currently understood to be a voltage which can be applied within the X-ray tube device. The X-ray tube device voltage can be applied between the cathode and the grid element and is in this case referred to as the X-ray tube device cut-off voltage. This can influence, in particular, the electron flow between the cathode and the anode, and in particular, prevent electrons from flowing from the cathode to the anode when the cutoff voltage of the X-ray tube device is applied. In this case, the grid element is preferably arranged between the anode and the cathode within the X-ray tube arrangement, viewed spatially and structurally. Typically, the grid element can be applied with an electrical potential relative to the cathode, which is more negative relative to the cathode. This prevents, in particular: electrons exiting from the cathode drift to the anode. In other words, the flow of electrons from the cathode to the anode can be inhibited or shut off, among other things.
Alternatively or additionally, an X-ray tube arrangement voltage can be applied between the anode and the cathode, whereby X-rays are typically generated at the anode. In general, the generation of X-rays can be inhibited or stopped by means of an X-ray tube device cut-off voltage when electrons flow out at the grid element, wherein the X-ray tube device voltage is also applied, for example, between the anode and the cathode. In other words, the X-ray tube device voltage and the X-ray tube device cut-off voltage are applied between the anode and the cathode, but no X-rays are generated or emitted at the anode.
In principle, it is also possible to consider: an X-ray tube device voltage can be applied between the electron emitter unit of the cathode and the at least one focusing electrode of the cathode. In this case, the X-ray tube device voltage is typically referred to as the X-ray tube device focus voltage. The electron emitter unit is especially configured for emitting electrons. The at least one focusing electrode is preferably designed to influence the electrons in such a way that the path of the electrons between the cathode and the anode is changed. In particular, the at least one focusing electrode is thus able to change the position or size of the focal spot, wherein typically the anode has the focal spot.
The control unit is designed to regulate and in particular to regulate the primary voltage in such a way that a predetermined secondary desired voltage is induced in the secondary coil, for example the already proposed X-ray tube device voltage, in particular the X-ray tube device voltage between the anode and the cathode, the X-ray tube device cut-off voltage and/or the X-ray tube device focus voltage. Furthermore, the control unit is designed such that the primary voltage is regulated as a function of the first and second measured voltages.
By adjusting the primary voltage as a function of the first and second measured voltages, it is preferably possible to: depending on the actual voltage at the secondary side, a specific measured value is determined at the primary side and is used, in particular, for regulating the primary voltage. In other words, the specific measured value, i.e. the actual voltage on the secondary side, is used as a control variable for the primary voltage to be regulated. In this case, the parasitic effects on the secondary side are taken into account in particular by the measuring element on the primary side. The following advantages are thereby achieved: the primary voltage can be set precisely such that the actual voltage on the primary side corresponds approximately to a predetermined desired voltage, in particular an ideal secondary voltage, on the secondary side, without the actual voltage on the secondary side being measured directly. In other words, the actual secondary-side actual voltage preferably deviates hardly from the ideal secondary voltage. In particular, the actual voltage on the actual secondary side deviates by less than 5%, preferably by less than 2% and particularly preferably by less than 1%, from the ideal secondary voltage or from a predetermined desired voltage on the secondary side. As a result, high voltage accuracies are achieved in particular, which are often important aspects in the medical field. Another advantage is that: the actual voltage on the secondary side can preferably be detected and/or regulated on the primary side independently of the load. This can be expressed in particular as: the actual voltage on the secondary side is not transmitted from the secondary side to the primary side across the galvanic separation point.
In particular, costly and cost-intensive transfers can be dispensed with, wherein the actual voltage of the secondary on the secondary side can be detected and transmitted to the primary side.
Preferably, the control unit has an evaluation unit. The evaluation unit is designed to determine the actual voltage on the secondary side on the basis of the first and second measured voltages. In this context, the control unit is preferably designed to regulate the primary voltage as a function of the actual voltage of the secondary. I.e. evaluating the unit output voltage value as an open loop control variable
Or closed-loop control variable
The voltage value corresponds to the determined value of the actual voltage on the secondary side. The actual voltage on the secondary side is also derived, in particular, approximately from the sum of the first and second measured voltages, which may each be provided with a weighting factor.
This makes it possible in particular to set the primary voltage and thus the actual voltage on the secondary side in a simple and load-independent manner. Load-independent is currently understood to mean in particular: it is possible to regulate the primary voltage as a function of the actual voltage of the secondary, independently of an electrical load, for example an X-ray tube arrangement, connected on the secondary side, i.e. at the secondary coil.
According to an alternative embodiment, the transformer unit can (also) have an additional auxiliary winding, which is preferably arranged in parallel with the primary coil. Such an auxiliary winding is used, for example, for the switch-on current limitation of the transformer unit and is not a mandatory component of the transformer unit.
For a sufficiently large inductance value of the auxiliary winding, the electrical current flow through the auxiliary winding can be neglected in determining the actual voltage on the secondary side. In this case, the actual voltage on the secondary side is preferably determined as already described above, i.e. as if the transformer unit had no auxiliary winding.
However, for the case in which the inductance value of the auxiliary winding is smaller than the inductance value which still allows the current flowing through the auxiliary winding to be ignored, the voltage drop (also referred to below as auxiliary voltage) over the auxiliary winding, which is dependent on the electrical current flow, is taken into account when determining the actual voltage on the secondary side.
In this case, consideration is preferably made such that the actual voltage on the secondary side is then determined by phase-correctly adding the auxiliary voltage to the first and second measured voltages. The summation for preferably determining the actual voltage on the secondary side is extended by a term which takes into account the (additional) voltage drop at the auxiliary winding.
The first and second measured voltages and the auxiliary voltage may in this case be provided with weighting factors, in each case, in a manner similar to the determination of the actual voltage on the secondary side described above.
According to one advantageous embodiment, the measuring element is designed as a second measuring coil, in particular depending on the type of compensation coil. A compensation coil is to be understood at present as a coil element which at least reduces the resonance occurring during operation of the transformer unit. Such resonances are, for example, voltage and/or current fluctuations.
However, measuring elements designed as measuring coils are currently not used or are not used only for compensating resonances. More precisely, the measuring coil is used to detect, in particular to measure, a second measuring voltage associated with a voltage drop (dependent on parasitic effects) on the secondary side.
For a more precise elucidation, the process and the operating principle, in particular the leakage losses of the transformer unit, are discussed in more detail below.
Usually, such leakage losses are used together to calculate an electrical variable of the transformer unit, for example a desired voltage of the secondary side. I.e. for example in the (equivalent) circuit diagram of a real transformer unit, the leakage losses are usually characterized/displayed by inductances, for example by coil elements. The characterization is based on the following considerations: the undesired voltage drop caused by leakage losses behaves like a voltage drop at the inductance. The inductance is typically referred to herein as leakage inductance. However, in a transformer unit, such leakage inductance does not exist as a real component.
The main aspects for this are also currently: an electrical balance between the primary side and the secondary side is preferably present in the transformer unit. Electrical balancing is currently understood as: for example, a voltage change on one side (primary side or secondary side) also causes a voltage change on the respective other side, which changes are then preferably in an equilibrium relationship with one another. That is, in the present example, the second measurement voltage on the primary side is linked via a variable to the (additional and undesired) voltage drop on the secondary side caused by the leakage magnetic losses. In other words: the second measurement voltage forms a mirror image (of the primary side) of the voltage dropped across the leakage inductance. In this case, the variables take into account, for example, the inductance values of the measuring element and the leakage inductance and the winding ratio formed by two of the first measuring coil, the primary coil and the secondary coil.
In principle, the inductance of the measuring element formed as a measuring coil can have any value. Preferably, the measuring element embodied as a measuring coil has an inductance with a value in the range from 500nH to 1000nH and in particular with a value in the range from 600nH to 800 nH. The measuring element thus has, in particular, a value of one tenth to one fifth of the usual compensation coil. Commonly used compensation coils typically have an inductance with a value in the range of 2 muh to 6 muh.
In a further development, the measuring element additionally also serves as a compensation coil, i.e. the characteristic values of the coil are suitably selected, in particular so that further compensation coils may be dispensed with.
Suitably, the measuring element is in series with the primary coil. In particular, a voltage drop, in this case the second measurement voltage, can thereby be determined, for example, by means of an evaluation unit.
According to a preferred refinement, the first measuring coil is terminated in a high-impedance manner. Terminating in a high-impedance manner is currently understood in particular to be: for example, the internal resistance of the first measuring coil has a value that is, for example, at least 5 to 10 times higher than the value of the internal resistance of the primary coil and/or the secondary coil. This modified form is based on the following considerations: since the first measuring coil is terminated in a high-impedance manner, a negligibly small coil current flows in the first measuring coil, which causes a negligible influence of the first measuring coil on electrical variables, for example the primary voltage and/or the actual voltage on the secondary side. In other words, the loading of the first measuring coil preferably does not occur, so that the coil current is preferably approximately zero. In this case, the coil current does not cause any further voltage drop, in particular.
According to a preferred embodiment, the evaluation unit has an amplifier element, preferably a differential amplifier element. The amplifier element is in particular designed such that it detects a second measurement voltage falling over the measurement element during operation. The advantages are that: this allows a simple and cost-effective voltage detection.
According to one advantageous embodiment, the evaluation unit has a first operational amplifier element. The first operational amplifier element is configured in particular for: the actual voltage on the secondary side is determined during operation from the first and second measured voltages. For this purpose, the second measured voltage is multiplied by a weighting factor, currently by the already mentioned variable, and then the two voltages (first and second measured voltage) are added by the operational amplifier. The design scheme has the advantages that: the determination of the actual voltage on the secondary side can be realized in a simple manner in terms of circuitry.
In the case of an alternative embodiment of the transformer unit having an auxiliary winding arranged in parallel with the primary winding, the first operational amplifier element is designed in particular to: the actual voltage on the secondary side is determined during operation from the first measured voltage, the second measured voltage and the auxiliary voltage. In this connection, the addition of the auxiliary voltage to the first and second measurement voltages, which has already been proposed in the above-described embodiments relating to the auxiliary winding, takes place by means of a first operational amplifier element.
In particular, the first operational amplifier element is configured as a summing amplifier element, also referred to simply as adder.
According to a preferred embodiment, the evaluation unit has a second operational amplifier element. The second operational amplifier element is configured as a peak detector. The peak value of the actual voltage on the secondary side determined by the first operational amplifier element is determined during operation, namely by means of the second operational amplifier element.
Expediently, a rectifier element for rectifying the actual voltage of the secondary side during operation of the transformer unit is present on the secondary side of the transformer unit.
Preferably, the control unit has an analog-to-digital converter element. The analog-to-digital converter element is designed such that it converts the determined actual voltage on the secondary side into a digital control signal. In other words, the actual voltage on the secondary side can be determined at least approximately on the primary side, taking into account the first and second measurement voltages, and converted into a digital control element by means of an analog-to-digital converter. That is to say, if instead of measuring the value of the actual voltage on the secondary side directly, the value of the actual voltage on the secondary side is preferably determined by means of a function of the first measured voltage and the second measured voltage. A digital control signal is understood to mean, in particular, at present: the value of the actual voltage on the secondary side is present after the conversion in the form of a predetermined number of zeros and ones, which can then be used more simply for regulating the primary voltage and thus for regulating the desired voltage of the secondary, for example by means of a microcontroller.
Alternatively or additionally, the control is effected, for example, as a function of an analog control signal. That is, the determined analog value of the actual voltage on the primary side is used, in particular, for regulating the primary voltage.
For regulating the primary voltage, the control unit has a switching power supply and at least two switching elements, preferably semiconductor switching elements, for example transistors.
In this case, the switching power supply preferably regulates the value of the primary voltage, and the at least two switching elements regulate the frequency of the primary voltage such that a desired secondary desired voltage is induced on the secondary side. In other words, the desired voltage of the secondary can be controlled in particular by controlling the primary voltage. The (drive) control of the switching power supply is additionally or alternatively carried out, for example, by means of an upstream microcontroller which controls the switching power supply on the basis of a digital control signal.
The experimental measurement shows that: by digitally adjusting the primary voltage, in particular based on the actual voltage on the secondary side, only deviations of the actual voltage from the desired and preset desired voltage of the secondary in the range of 1% to 2% occur.
According to one advantageous embodiment, the switching power supply is designed as a single-ended primary inductor converter (SEPIC converter). Alternatively, the switching power supply is designed as a step-up converter or as a step-down converter.
The advantage of this embodiment can be, in particular, a simple and cost-effective design of the switching power supply, since conventional (ground) components are used for its implementation.
Preferably, the transformer unit is provided in an X-ray apparatus and is used in particular for providing an X-ray tube device voltage. In other words, it is preferred that the X-ray device has a transformer unit. The X-ray device can have other typical elements for X-ray imaging, such as an X-ray detector.
According to the invention, the object is achieved for a method for operating a transformer unit having the features of the invention. The transformer unit is in particular the described transformer unit.
In operation, a primary winding wound around the transformer core on the primary side is acted upon by a primary voltage via a control unit, and the actual voltage on the secondary side is set, in particular induced, in the secondary winding. Typically, the actual voltage on the secondary side is influenced, in particular reduced, by an additional voltage source on the secondary side, which is dependent on parasitic effects on the secondary side.
The first measurement voltage is determined via a first measurement coil which is also arranged around the transformer core in a subregion of the primary side of the transformer unit. Furthermore, the transformer unit has a measuring element which is arranged on the primary side such that a second measurement voltage which is associated with the voltage drop on the secondary side is determined via the measuring element.
The operation of the transformer unit is preferably controlled by means of a control unit such that the primary voltage is regulated in order to induce a predetermined secondary desired voltage in the secondary winding. Furthermore, the operation of the transformer unit is controlled by means of the control unit, in particular, in such a way that the primary voltage is regulated as a function of the first and second measured voltages.
The advantages and preferred embodiments described in detail with respect to the transformer unit can also be transferred to the method in terms of meaning and vice versa.
Drawings
Hereinafter, embodiments of the present invention are explained in detail with reference to the drawings. The drawing parts are shown in an extremely simplified view:
fig. 1 shows a roughly sketched equivalent circuit diagram of a transformer unit.
Detailed Description
Fig. 1 shows a roughly sketched equivalent circuit diagram of a transformer unit 2. Equivalent circuit diagrams are used, in particular, in electronics, for example, for calculating electrical variables within an electrical circuit. The equivalent circuit diagram is characterized in that: it shows a circuit in which also non-really built components are contained, which act on the switching behavior of the circuit. For example, an equivalent circuit diagram has components that (representatively) characterize the losses that occur within the circuit.
The transformer unit 2 has a primary side 4 with a primary coil 6 and a secondary side 8 with a secondary coil 10. The primary coil 6 and the secondary coil 10 are preferably of an electrically conductive material, in this embodiment of copper. An X-ray tube device 12 of an X-ray apparatus 11 is further connected to the secondary coil 10 on the secondary side. In particular, the X-ray tube arrangement 12 has a cathode 14 and an anode 16 in this embodiment. The X-ray tube device 12 further includes a grid element 17. A grid element 17 is arranged between the cathode 14 and the anode 16.
The transformer unit 2 is used in this embodiment for providing the X-ray tube device voltage UR. In operation, at the cathode when requiredApplying an X-ray tube device voltage U between 14 and a grid element 17RIn this embodiment the X-ray tube device, cuts off the voltage and prevents the flow of electrons from the cathode 14 to the anode 16.
Since a dc voltage is required in particular for the cut-off voltage of the X-ray tube device, the transformer unit 2 has a rectifier element 42 on the secondary side 8. The rectifier element 42 serves for rectifying the actual voltage of the secondary (which corresponds to the X-ray tube device voltage U)RAnd in this case corresponds to the X-ray tube device cut-off voltage) and is arranged spatially and structurally between the secondary coil 10 and the X-ray tube device 12.
In the equivalent circuit diagram according to fig. 1, an inductive element 18 is arranged between the secondary coil 10 and the X-ray tube arrangement 12. The inductive element 18 is a leakage inductance in this embodiment. The secondary inductance describes the leakage losses occurring on the secondary side within the equivalent circuit diagram, so that they can be used for the calculation.
In this respect, in this embodiment, the voltage drop over the leakage inductance is taken into account. The inductive element 18 is not provided as a real component in the transformer unit 2. Voltage drop U at leakage inductanceL(also referred to as additional secondary voltage drop) changes, namely: increasing or decreasing the desired voltage U of the secondarySSuch that the actual voltage U on the secondary sideSIThe actual voltage applied to the secondary side of the X-ray tube arrangement 12 is greatly simplified from the ideal actual voltage of the secondary and the voltage drop U above the leakage inductanceLThe difference between them.
A first measuring coil 20 is arranged on the primary side 4 of the transformer unit 2. The first measurement voltage U can be detected by means of the first measurement coil 20M. Primary voltage UPIs the voltage to which the primary winding 6 is charged when the transformer unit 2 is in operation. For this purpose and in order to form the function of the transformer unit 2, the primary coil 6, the secondary coil 10 and the first measuring coil 20 are wound around the transformer core 24. The transformer core 24 has a ferromagnetic material, such as iron. In operation, according to the law of induction, by means of a primary voltage UPInducing a desired voltage of the secondary in the secondary coilUS。
Furthermore, a measuring element 26, in this example a second measuring coil 22, is provided as a real component on the primary side 4. The measuring element 26 is shown in the equivalent circuit diagram according to fig. 1 as an inductive element and thus with the usual circuit symbol of an inductive element. The measuring element 26 in this exemplary embodiment has an inductance with a value in the range from 500nH to 1000nH, which is limited in particular by a compensation coil, which is usually also arranged on the primary side.
The transformer unit 2 also has a control unit 34. The control unit 34 has an evaluation unit 28 in this exemplary embodiment. The evaluation unit 28 is designed in this exemplary embodiment to: determining the actual voltage U of the secondary sideSI. For this purpose, the evaluation unit 28 has an amplifier element 30, which in this exemplary embodiment has a device for detecting a second measurement voltage U across the measurement element 26METhe differential amplifier of (1).
Furthermore, the evaluation unit 28 has a first operational amplifier element 32 which has two inputs (Op1, Op 2). In this exemplary embodiment, the first operational amplifier element 32 is designed as a summing amplifier, in particular as an adder, which sums the signals applied to the input terminals Op1 and Op2, respectively. In this embodiment, the first measurement voltage UMIs applied at an input Op1 and a second measurement voltage UMEIs applied at input Op2 so that the two voltage values add to the output value. The output value of the first operational amplifier element 32 is transmitted during operation to a second operational amplifier element 33, which is likewise part of the evaluation unit 28. The second operational amplifier element 33 is in this embodiment configured as a peak detector. In operation, the second operational amplifier element 33 determines the peak value of the output value delivered by the first operational amplifier element 32. The output value of the second operational amplifier element 33 therefore preferably corresponds in this exemplary embodiment to the actual voltage U on the secondary sideSIPeak value of (a). For a better understanding, the electrical relations within the transformer unit 2 are briefly discussed below:
by calculating each (sub) within the transformer unitVoltage and (sub) current and suitable mesh and node formation taking into account the electrical ratio of the primary side 4 to the secondary side 8 can be achieved by measuring the voltage U from the first measurement voltage UMAnd a second measurement voltage U multiplied by a weighting factor GMEFormed to determine the actual voltage U of the secondary sideSIAbsolute value of (a). Here, the weighting factor G takes into account the inductance values of the individual measuring elements 26 and inductive elements 18 and the winding ratios of the primary coil 6, secondary coil 10 and first measuring coil 20. From this, the actual voltage U on the secondary side can be derivedSIAnd two measurement voltages UM、UMEThe following relationships between:
USI/ü23＝-G*UME+UM
here, u23The winding ratio of the first measuring coil 20 to the secondary coil 10 is described. The weighting coefficient G is composed as follows:
G＝(Ls2*ü12)/(LME*ü23)
where L isS2Describing the value of the leakage inductance of the secondary side, and12the winding ratio of the primary coil 6 to the secondary coil 10 is described. Coefficient LMEThe induced values of the second measuring coil 22 are described here.
The transformer unit 2 has an auxiliary winding (not shown) arranged in parallel with the primary winding 6, and an auxiliary voltage U can be dropped during operation at said auxiliary windingHAnd the induced value of the auxiliary winding is less than the inductance value which just still allows to ignore the current flowing through the auxiliary winding, the actual voltage U on the secondary side can be deducedSITwo measurement voltages UM、UMEAnd an auxiliary voltage UHThe following relationships between:
USI/ü23＝-G*UME+UM+UH
here, UHConsists of the following components:
UH＝Ls2*(N1 2/N2 2)*(UM/LM)
here, N is1The number of turns of the auxiliary winding is described,N2the number of turns of the secondary coil 10 is described, and LMThe value of the main inductance is described.
Forming the mesh and the nodes is currently understood as an application of kirchhoff's law according to which the sum of the (sub) voltages falling within one mesh is equal to zero and the sum of the (sub) currents flowing in and out of one node is equal to zero. A mesh is currently understood to be a closed loop along an electrical conductor within an electrical circuit. A node is currently understood to be a branch within a circuit from which at least three conductors branch.
The electrical ratio between the primary side 4 and the secondary side 8 is currently understood to be, for example: from the primary voltage UPAnd the turns ratio of the number of turns of the secondary coil 10 to the number of turns of the primary coil 6, the desired voltage U of the secondary can be determinedS。
The control unit 34 is in this embodiment also adapted to determine the actual voltage U on the secondary side based on thisSITo regulate the primary voltage UP. For this purpose, the control unit 34 has an analog-digital converter element 36, a switching power supply 38 and at least two switching elements 40. The analog-to-digital converter element 36 is configured in this embodiment to: determining the actual voltage U of the secondary sideSIIs converted into a digital control signal S. The switching power supply 38 is designed in this exemplary embodiment as a single-ended primary inductor converter (SEPIC converter) and regulates the primary voltage U as a function of the control signal SPThe value of (c). Alternatively, the switching power supply 38 is designed as a step-up converter or as a step-down converter. At least two switching elements 40 for generating an alternating voltage as a primary voltage UP. In this exemplary embodiment, the switching element 40 is in the form of a semiconductor switch, for example a transistor.
Experimental measurements and simulations show that: actual voltage U on the secondary side generated by means of transformer unit 2 according to fig. 1SIWith a preset desired voltage USWith a deviation in the value in the range of 1.5% to 2.5%. The deviation value is also observed for different electrical loads connected on the secondary side. The load connected on the secondary side is currently understood as an X-ray tube device 12, for example.
The subject matter of the invention is not limited to the embodiments described above. Rather, further embodiments of the invention can be derived from the above description by a person skilled in the art. In particular, the individual features of the invention described in relation to the different exemplary embodiments and their design variants can also be combined with one another in other ways.
Claims (17)
1. A transformer unit (2), wherein the transformer unit (2) has:
-a primary side (4) having a primary coil (6) wound around a transformer core (24) and a secondary side (8) having a secondary coil (10) wound around the transformer core (24), wherein in operation a primary voltage (U) is applied to the primary coil (6)P) While generating the actual voltage (U) of the secondary sideSI) The actual voltage of the secondary side is due to an additional voltage drop (U) of the secondary side which depends on parasitic effects of the secondary sideL) Is subjected to the influence of the pressure on the air,
-a first measuring coil (20) wound around the transformer core (24) for determining a first measuring voltage (U)M)，
A measuring element (26) which is arranged and designed on the primary side (4) such that a second measuring voltage (U) is determined via the measuring element (26)ME) The second measurement voltage and the additional voltage drop (U) on the secondary sideL) Are associated with, and
a control unit (34) for controlling the operation of the transformer unit (2), wherein the control unit (34) is designed to,
-causing the primary voltage (U) to be regulatedP) In order to induce a predetermined secondary desired voltage (U) in the secondary coil (10)S)，
-and such that it is dependent on said first measurement voltage (U)M) And the second measurement voltage (U)ME) Regulating the primary voltage (U)P)，
Wherein the control unit (34) has an evaluation unit (28) which is designed to determine the first measurement voltage (U)M) And saidSecond measurement voltage (U)ME) Determining the actual voltage (U) of the secondary sideSI) And wherein the control unit (34) is designed to determine the actual voltage (U) of the secondary side as a function of the determined voltageSI) Regulating the primary voltage (U)P)。
2. Transformer unit (2) according to claim 1,
wherein the transformer unit (2) is used for providing an X-ray tube device voltage (U) for an X-ray apparatus (11)R)。
3. Transformer unit (2) according to claim 1 or 2,
wherein an auxiliary winding is arranged in parallel with the primary coil, and the evaluation unit (28) is designed to evaluate the first measurement voltage (U)M) The second measurement voltage (U)ME) And an auxiliary voltage dropped across the auxiliary winding, determining the actual voltage (U) on the secondary sideSI)。
4. Transformer unit (2) according to claim 1 or 2,
wherein the measuring element (26) is designed as a second measuring coil (22).
5. Transformer unit (2) according to claim 1 or 2,
wherein the actual voltage (U) of the secondary sideSI) And a preset desired voltage (U) of said secondaryS) The deviation therebetween is less than 5%.
6. Transformer unit (2) according to claim 1 or 2,
wherein the measuring element (26) is connected in series with the primary coil (6).
7. Transformer unit (2) according to claim 1 or 2,
wherein the first measuring coil (20) terminates in a high-impedance manner.
8. Transformer unit (2) according to claim 1 or 2,
an amplifier element (30) is provided, which is designed in such a way that, during operation, it detects the second measurement voltage (U) falling across the measurement element (26)ME)。
9. Transformer unit (2) according to claim 1 or 2,
wherein the evaluation unit (28) has a first operational amplifier element (32) which is designed such that it is driven from the first measurement voltage (U)M) And the second measurement voltage (U)ME) Determining the actual voltage (U) of the secondary sideSI)。
10. Transformer unit (2) according to claim 9,
wherein the first operational amplifier element (32) is configured as a summing amplifier element.
11. Transformer unit (2) according to claim 1 or 2,
wherein the evaluation unit (28) has a second operational amplifier element (33) which is designed as a peak detector.
12. Transformer unit (2) according to claim 1 or 2,
wherein the control unit (34) has an analog-digital converter element (36) which is designed in such a way that it will determine the actual voltage (U) on the secondary sideSI) Converted into a digital control signal (S).
13. Transformer unit (2) according to claim 1 or 2,
wherein the control unit (34) has a switching power supply (38) and at least two switching elements (40), wherein the switching power supply (38) and the at least two switching elements are used to switch on(40) According to the actual voltage (U) of the secondary sideSI) Regulating the primary voltage (U)P)。
14. Transformer unit (2) according to claim 13,
wherein the switching power supply (38) is configured as a single-ended primary inductor converter.
15. Transformer unit (2) according to claim 1 or 2,
the transformer unit is arranged in an X-ray apparatus (11) for providing an X-ray tube device voltage (U)R)。
16. A method for operating a transformer unit (2), wherein
-the transformer unit (2) has a primary side (4) with a primary coil (6) wound around a transformer core (24) and a secondary side (8) with a secondary coil (10) wound around the transformer core (24), and the primary coil (6) is loaded with a primary voltage (U)P) So that the actual voltage (U) of the secondary side is generatedSI) The actual voltage of the secondary side is due to an additional voltage drop (U) of the secondary side which depends on parasitic effects of the secondary sideL) Is subjected to the influence of the pressure on the air,
-using a first measuring coil (20) wound around the transformer core (24) for determining a first measuring voltage (Uj)M)，
-determining a voltage drop (U) with the secondary side by means of a measuring element (26) arranged on the primary side (4)L) Associated second measurement voltage (U)ME)，
-based on said first measurement voltage (U)M) And the second measurement voltage (U)ME) Determining the actual voltage (U) of the secondary sideSI) And is
-determining the actual voltage (U) of the secondary side based on the determined voltageSI) Regulating the primary voltage (U)P) So that a predetermined secondary desired voltage (U) is induced in the secondary coil (10)S)。
17. The method of claim 16, wherein the first and second light sources are selected from the group consisting of,
wherein the method is used for providing an X-ray tube arrangement voltage (U) for an X-ray apparatus (11)R)。
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102017220991.7 | 2017-11-23 | ||
| DE102017220991.7A DE102017220991B4 (en) | 2017-11-23 | 2017-11-23 | Transformer unit and method for operating a transformer unit |
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| Publication Number | Publication Date |
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| CN109905033A CN109905033A (en) | 2019-06-18 |
| CN109905033B true CN109905033B (en) | 2021-04-02 |
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| CN201811407351.9A Active CN109905033B (en) | 2017-11-23 | 2018-11-23 | Transformer unit and method for operating a transformer unit |
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| US (1) | US10455676B2 (en) |
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| US11751316B2 (en) * | 2019-11-05 | 2023-09-05 | Gulmay Limited | Power transfer and monitoring devices for X-ray tubes |
| FR3112870B1 (en) * | 2020-07-21 | 2022-08-26 | Vitesco Technologies | Device for automatic detection of coupling between electronic devices |
| DE102020210118B4 (en) | 2020-08-11 | 2022-03-24 | Siemens Healthcare Gmbh | Controlling an X-ray tube |
| DE102022206833A1 (en) | 2021-09-01 | 2023-03-02 | Siemens Healthcare Gmbh | Operating an X-ray tube |
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- 2018-11-23 CN CN201811407351.9A patent/CN109905033B/en active Active
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| US4200796A (en) * | 1977-06-17 | 1980-04-29 | Hitachi Medical Corporation | Storage cell type X-ray apparatus |
| US5138543A (en) * | 1991-05-31 | 1992-08-11 | At&T Bell Laboratories | Output voltage estimating circuit for a power converter having galvanic isolation between input and output circuits |
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Also Published As
| Publication number | Publication date |
|---|---|
| DE102017220991B4 (en) | 2022-10-06 |
| DE102017220991A1 (en) | 2019-05-23 |
| CN109905033A (en) | 2019-06-18 |
| US10455676B2 (en) | 2019-10-22 |
| US20190159326A1 (en) | 2019-05-23 |
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Effective date of registration: 20240902 Address after: German Phu F Haim Patentee after: Siemens Medical AG Country or region after: Germany Address before: Erlangen Patentee before: SIEMENS HEALTHCARE GmbH Country or region before: Germany |